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OBJECTIVES
• Learn how to manage patients with single and multiple cystic conditions of the kidney (diet / lifestyle, blood pressure, imaging, follow-up, drug therapy)
• Learn what types of kidney stones can form and prevalence of each
• Learn how to prescribe effective preventive therapy for different stone types
CYST CLASSIFICATION – DISTRIBUTION / SIZE / NUMBER
• Simple cysts • Complex cysts • PCKD
– Autosomal recessive – Autosomal dominant
• Acquired renal cystic disease • Medullary Sponge Kidney • Medullary Cystic disease
(‘Autosomal Dominant Interstitial Kidney Disease’)
• Other – von Hippel Lindau – Tuberous sclerosis
SIMPLE CYSTS • Incidence:
– Varies by population, age (highest in older males) – < 1% below age 30; 30% above 70
• Bilateral in 9% > 70 years • Histopathology:
– Single epithelial cell layer, clear or straw coloured fluid within resembling plasma
• Significance: – ? None – Some case series association with hyperfiltration, mild renal
impairment, hypertension, albuminuria – Complications rare: Renin-induced hypertension, infection, bleeding
(gross hematuria +/- flank pain), obstruction • No follow-up imaging necessary
Rule AD et al. AJKD 2012;59(5):611
POLYCYSTIC KIDNEY DISEASE
Cyst criteria for diagnosis if family history known: - 15-39: 3+ cysts unilateral or bilateral - 40-59: 2+ cysts per kidney - 60+: 4+ cysts per kidney If family history unknown: no definite number for unequivocal diagnosis, but 10+ per kidney ‘strongly suspect’ Pei Y et al. JASN 2009;20(1):25
PCKD - FEATURES • Incidence: 1/400 • Renal +/- liver (about 50%) +/- pancreatic cysts • Cyst complications
– Bleeding (gross hematuria +/- flank pain), infection, renin-induced hypertension, obstruction, stones
• Mass effects – Fullness/bloating, early satiety; transplant considerations
• Hypertension – Renin-induced – Renal parenchymal
• Extra-renal manifestations: – Intracranial aneurysm (incidence 5% < 30 yrs, 20% >60 yrs) – Inguinal hernia – Cardiac valvular: Mitral valve prolapse >> AR – AAA – possibly higher risk – Renal Cell Carcinoma- possibly higher risk
• Renal Failure
Chapman AB et al NEJM 1992;327(13):916)
PCKD – RENAL FAILURE • Incidence ESRD 6 PMP; ?majority with PCKD • Comprise 5-10% of prevalent HD patients in Canada • Once renal function drops, rate -5 mL/min/year • Higher risk of ESRD if:
– Pt factors: Genetics (PCKD1 >> PCKD2), male, low birth weight – Clinical factors – HTN:
• GFR > 60, age < 50 aim BP 95/60 – 110/70, choose ACE inhibitor (Schrier R et al, NEJM Nov 2014)
• GFR 25-60, aim BP 110/70 – 130/80, choose ACE inhibitor (Torres V et al, NEJM Nov 2014)
– Imaging factors: Nephromegaly – Laboratory factors: albuminuria, hyperuricemia, increased urine sodium
excretion, increased plasma copeptin level (surrogate for vasopressin) • Treatment
– Diet / lifestyle: ? Protein restriction; low Na; fluids > 3L/day, avoid caffeine – BP control: ACE inhibitors 1st line; BP target – ? mTOR inhibitors, somatostatin, vasopressin receptor antagonists – Rarely nephrectomy required
Torres et al. KI 2009;76(2):149
NEPHROLITHIASIS – A PAINFUL PROBLEM!
• Affects approx 10% of adults – Slight male predominance
• Incidence varies geographically • Approx 50% have one or more recurrence at 10 years
– Detailed evaluation generally performed for recurrent stone formers
• Can cause significant morbidity • Rare cause of end-stage kidney failure
TYPES OF STONES • Calcium
– Calcium oxalate – Calcium phosphate
• Uric acid • Struvite ‘staghorn’
– Magnesium ammonium phosphate
• Drug-related – Creation of metabolic environment favouring
stone formation – Crystallization of drug itself when
supersaturated in urine
• Rare Stone Disorders: – APRT Deficiency, Dent Disease, Cystinuria,
Primary hyperoxaluria
CalciumUric acidStruviteDrugCystineOther
HOW CAN I TELL WHAT TYPE OF STONE MY PATIENT HAS?
• History – Age, comorbidities, medications, family history, occupation /
environment, prior kidney or GI surgery • Physical
– Urinalysis • presence of crystals
• Lab testing – Serum: creatinine, bicarbonate, calcium, PTH, glucose/HgA1c, uric acid – Urine (24 hr): calcium, uric acid, oxalate, sodium, citrate – Urine pH: uric acid crystals form in acidic uric, calcium phosphate
crystals form in alkaline urine, urine is alkaline with struvite stones • Imaging:
– Radiolucent (uric acid stones) vs opaque (most other stones) – ? Nephrocalcinosis
• Stone Analysis
SELECTED MEDICATIONS • Change urine pH or composition:
– Vitamin C – Vitamin D – Calcium (ie. CaCO3) – Diuretics: carbonic anhydrase inhibitors, loop diuretics, other
(common OTC herbal remedies)
• Drug precipitates: – Antimicrobials: acyclovir, amoxicillin, ampicillin, ceftriaxone,
ciprofloxacin, sulfamethoxazole • Protease inhibitors: indinavir
– Guaifenesin – Triamterene – Methotrexate
CALCIUM OXALATE
• Most common (80-85%) • Presumed diagnosis unless
atypical features • Higher incidence:
– Post (partial) bowel resection – High dose Vitamin C – Family history
• Hypercalciuria not necessary
• Hyperoxaluria not necessary
URIC ACID STONES
• Reasonably common • Risk factors:
– Gout – Chronic diarrhea – Obesity – Metabolic syndrome / DM – Malignancy
• Not seen on plain X-ray • Hyperuricosuria common
STRUVITE STONES
• Magnesium ammonium phosphate + calcium carbonate
• Formed in infected upper urinary tract: – Females, neurogenic bladder, urinary
diversion – Can grow quickly so often present late
• UTI symptoms, flank pain, gross hematuria
• pH > 7 • Antibiotics and surgical removal required
CYSTINE STONES
• Cystinuria 1/7000 live births – Reduced renal absorption cystine
(plus ornithine, lysine, arginine)
• +/- Family history • Often presents in childhood • Can form staghorn calculi • Less radiopaque than calcium
stones
WHAT PROVEN TREATMENTS ARE THERE?
• Increasing fluid intake • Thiazide diuretic (reduces urine calcium) • Allopurinol (reduces urine uric acid) • Citrate (raises urine citrate / raises urine pH)
OTHER TREATMENTS • Diet • Oral calcium (oxalate binding) • Disease-specific
– ie. captopril or penicillamine for cystinuria • Analgesia • Alpha blockers (relax smooth muscle tone of ureters to help
stone pass / relieve colic) • Lithotripsy • Surgical
– Endoscopic – Percutaneous – Open
• MEDICAL THERAPY DOES NOT DISSOLVE STONES
DIET - SUMMARY Diet Parameter Goal (daily)
Fluid Enough for urine output > 2.5 L Sodium < 2000 mg, possibly lower Calcium 800-1200 mg (NOT restricted!) Oxalate 40-50 mg Citrate ? Specific target Protein < 6 oz
Vitamin C < 1000 mg
Case 1 - Patient AS
• 34 F 4 year history of recurrent nephrolithiasis, onset with renal colic at age 26 when pregnant – Every 6 months, then monthly severe colic – Stone obstruction twice (9mm, 1.2cm); bilateral ureteric
obstruction with urosepsis – Ureteric stents placed on multiple occasions
• No family history • CT-KUB consistent with medullary sponge kidneys;
multiple bilateral calculi up to 3 mm in size
AS - continued
• Normal serum biochemistry • Stone analysis: calcium oxalate • Urinalysis: pH 6.5, RBC 40-100/hpf • 24 hr urine:
– Volume 3.7 L – Calcium 5.2 (2.2-6.5 mmol/d) – Oxalate 344 (40-340 umol/d) – Citrate 4.44 (0.7-4.9 mmol/d) – Sodium 207 (40-220 mmol/d) – Uric acid 3.4 (1-3.8 mmol/d)
AS – follow-up 3 years later…
• Therapy: – HCTZ 12.5 mg po BID – Potassium citrate 50 mEq po TID – Prazosin 1 mg po OD – Cipro 500 mg po OD – Endoscopic stone extraction & laser lithotripsy x2
• Urine pH 8.5 • Urine volume still high, biochemistry still normal • Right hydronephrosis with multiple impacted ureteric
stones – currently awaiting surgery
Case 2 – Patient WM
• 32 F of Chinese descent, presented with creatinine 106 on routine lab testing – U/S: nephrocalcinosis, bilateral hydronephrosis, cortical
thinning – CT: staghorn calculi bilaterally, multiple intrarenal stones
• Extensive surgery / subsequent surgeries • Pregnancy with nephrolithiasis complicating • Urine amino acid electrophoresis: urine cystine
excretion 4x normal • Increased fluids, diet control, and K citrate
OBJECTIVES REVISITED
• Learn how to manage patients with single and multiple cystic conditions of the kidney (diet / lifestyle, blood pressure, imaging, follow-up, drug therapy)
• Learn what types of kidney stones can form and prevalence of each
• Learn how to prescribe effective preventive therapy for different stone types